Jeep Cherokee

Neutral Safety Switch Repair Procedure

Because mis-alignment, corrosion, and dust or water entering the Shift Position Sensing Unit (AKA Neutral Safety) switch can cause a multitude of  malfunctions of the AW4 automatic transmission, it is a good idea to check it out before assuming you have a bad transmission or Transmission Control Unit. These problems may be intermittent so can be very hard to pin down at times.  The switch is quite expensive to purchase a new one, but is easily adjusted or taken apart and cleaned. 

You can check out the switch before removing it from the transmission by using a ohmmeter at the plug where it connects to the wiring harness. The plug is located on the passenger side of the engine compartment next to the firewall. You should read continuity according to the instructions below.  If you read any resistance and not total continuity in any of the pins on the plug when moving the shift lever then remove the switch and clean it.  Be sure you are on level ground with the parking brake set, the wheels blocked, and engine off prior to testing or removal of the switch. The instructions from the Cherokee Repair manual for removal, replacement and adjustment are found below. 

Note: Part of the switch housing is a plastic material.  When removing the switch it may be hard to slide off of the shaft because of a build up of dirt and corrosion.  You may want to spray it with a penetrating oil and let it set for a while before trying to remove it.  Be careful when prying it off of the shaft or the plastic housing may crack.

The pictures of the disassembled switch are courtesy of  Frank Barnes, who had installed the CompuShift Plus but still had shift problems.  I suggested to him that it might be the 1-2 position switch on the transmission that was causing him problems so he said he would check it.  What he found is that the switch was, as he put it, "full of crap" and was causing intermittent transmission and backup light operation.  

Because of the fact that the switch has eight separate contacts and two sets of wipers you can have problems in only one area of the switch and circuit while everything else functions fine.  So you cannot just assume that if it starts ok in park or neutral that all of the rest of the contacts are fine. 

The switch is held together by Phillips screws and is not sealed so it can be taken apart quite easily.  After removing the screws it is a simple matter of removing the wiper arm and its two springs and contacts.  You can then use a contact cleaner to spray both halves of the switch assembly taking care to make sure that all the contact surfaces on it and the wiper arm are clean and bare. Replace the springs and contacts into the wiper arm and reassemble it to the case with the contacts on the wiper arm facing the contacts on the wired side of the assembly then apply a light lube or grease to the arm where it goes through the hole in the other half of the assembly and also to the back side of it (opposite the contacts) where it rides on the assembly case. Take care not to get any on the contacts themselves. If you wish use a light silicone or other sealant on the edges of the case before tightening the screws. This will help to keep out any new contamination.  Re-install and adjust the switch according to the directions below.

Disassembled Neutral Safety/Back Up and 1-2 Switch

Transmission Position Sensing Unit Connector.

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